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<h1 id="sec_name">
<span data-if="hdevelop" style="display:inline;">fread_char</span><span data-if="c" style="display:none;">T_fread_char</span><span data-if="cpp" style="display:none;">FreadChar</span><span data-if="dotnet" style="display:none;">FreadChar</span><span data-if="python" style="display:none;">fread_char</span> (算子名称)</h1>
<h2>名称</h2>
<p><code><span data-if="hdevelop" style="display:inline;">fread_char</span><span data-if="c" style="display:none;">T_fread_char</span><span data-if="cpp" style="display:none;">FreadChar</span><span data-if="dotnet" style="display:none;">FreadChar</span><span data-if="python" style="display:none;">fread_char</span></code> — Read one character from a text file.</p>
<h2 id="sec_synopsis">参数签名</h2>
<div data-if="hdevelop" style="display:inline;">
<p>
<code><b>fread_char</b>( :  : <a href="#FileHandle"><i>FileHandle</i></a> : <a href="#Char"><i>Char</i></a>)</code></p>
</div>
<div data-if="c" style="display:none;">
<p>
<code>Herror <b>T_fread_char</b>(const Htuple <a href="#FileHandle"><i>FileHandle</i></a>, Htuple* <a href="#Char"><i>Char</i></a>)</code></p>
</div>
<div data-if="cpp" style="display:none;">
<p>
<code>void <b>FreadChar</b>(const HTuple&amp; <a href="#FileHandle"><i>FileHandle</i></a>, HTuple* <a href="#Char"><i>Char</i></a>)</code></p>
<p>
<code>HString <a href="HFile.html">HFile</a>::<b>FreadChar</b>() const</code></p>
</div>
<div data-if="com" style="display:none;"></div>
<div data-if="dotnet" style="display:none;">
<p>
<code>static void <a href="HOperatorSet.html">HOperatorSet</a>.<b>FreadChar</b>(<a href="HTuple.html">HTuple</a> <a href="#FileHandle"><i>fileHandle</i></a>, out <a href="HTuple.html">HTuple</a> <a href="#Char"><i>charVal</i></a>)</code></p>
<p>
<code>string <a href="HFile.html">HFile</a>.<b>FreadChar</b>()</code></p>
</div>
<div data-if="python" style="display:none;">
<p>
<code>def <b>fread_char</b>(<a href="#FileHandle"><i>file_handle</i></a>: HHandle) -&gt; str</code></p>
</div>
<h2 id="sec_description">描述</h2>
<p>该算子 <code><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></code> reads a character from the input
file defined by <a href="#FileHandle"><i><code><span data-if="hdevelop" style="display:inline">FileHandle</span><span data-if="c" style="display:none">FileHandle</span><span data-if="cpp" style="display:none">FileHandle</span><span data-if="com" style="display:none">FileHandle</span><span data-if="dotnet" style="display:none">fileHandle</span><span data-if="python" style="display:none">file_handle</span></code></i></a>.
The input file must have been opened with <a href="open_file.html"><code><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></code></a> in text format.
</p>
<p>The read character or the control character sequence 'eof' is returned in
parameter <a href="#Char"><i><code><span data-if="hdevelop" style="display:inline">Char</span><span data-if="c" style="display:none">Char</span><span data-if="cpp" style="display:none">Char</span><span data-if="com" style="display:none">Char</span><span data-if="dotnet" style="display:none">charVal</span><span data-if="python" style="display:none">char</span></code></i></a>.
该算子 <code><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></code> respects the encoding of the characters,
unless the file was opened with the option <i><span data-if="hdevelop" style="display:inline">'ignore_encoding'</span><span data-if="c" style="display:none">"ignore_encoding"</span><span data-if="cpp" style="display:none">"ignore_encoding"</span><span data-if="com" style="display:none">"ignore_encoding"</span><span data-if="dotnet" style="display:none">"ignore_encoding"</span><span data-if="python" style="display:none">"ignore_encoding"</span></i>
(see <a href="open_file.html"><code><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></code></a>).
Thus, when opened with the correct encoding 该算子 <code><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></code>
returns multi-byte characters at once.
If necessary, the character is transcoded into the current encoding of the
HALCON library (see <a href="set_system.html"><code><span data-if="hdevelop" style="display:inline">set_system(::'filename_encoding',&lt;encoding&gt;:)</span><span data-if="c" style="display:none">set_system("filename_encoding",&lt;encoding&gt;)</span><span data-if="cpp" style="display:none">SetSystem("filename_encoding",&lt;encoding&gt;)</span><span data-if="com" style="display:none">SetSystem("filename_encoding",&lt;encoding&gt;)</span><span data-if="dotnet" style="display:none">SetSystem("filename_encoding",&lt;encoding&gt;)</span><span data-if="python" style="display:none">set_system("filename_encoding",&lt;encoding&gt;)</span></code></a>).
</p>
<p>When the file was opened with encoding mode <i><span data-if="hdevelop" style="display:inline">'ignore_encoding'</span><span data-if="c" style="display:none">"ignore_encoding"</span><span data-if="cpp" style="display:none">"ignore_encoding"</span><span data-if="com" style="display:none">"ignore_encoding"</span><span data-if="dotnet" style="display:none">"ignore_encoding"</span><span data-if="python" style="display:none">"ignore_encoding"</span></i>,
<a href="#Char"><i><code><span data-if="hdevelop" style="display:inline">Char</span><span data-if="c" style="display:none">Char</span><span data-if="cpp" style="display:none">Char</span><span data-if="com" style="display:none">Char</span><span data-if="dotnet" style="display:none">charVal</span><span data-if="python" style="display:none">char</span></code></i></a> always returns one byte without any interpretation or
transcoding. This is useful for reading a file with special control bytes
in a kind of raw mode.
If no character can be read because the end of the file is reached,
<code><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></code> returns the control character sequence <i><span data-if="hdevelop" style="display:inline">'eof'</span><span data-if="c" style="display:none">"eof"</span><span data-if="cpp" style="display:none">"eof"</span><span data-if="com" style="display:none">"eof"</span><span data-if="dotnet" style="display:none">"eof"</span><span data-if="python" style="display:none">"eof"</span></i> in
<a href="#Char"><i><code><span data-if="hdevelop" style="display:inline">Char</span><span data-if="c" style="display:none">Char</span><span data-if="cpp" style="display:none">Char</span><span data-if="com" style="display:none">Char</span><span data-if="dotnet" style="display:none">charVal</span><span data-if="python" style="display:none">char</span></code></i></a>.
</p>
<p>该算子 <code><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></code> emits a low-level error message, when
the next byte or byte sequence does not represent a valid code point in the
specified encoding. Despite of the low-level error message, 该算子
will not fail and <a href="#Char"><i><code><span data-if="hdevelop" style="display:inline">Char</span><span data-if="c" style="display:none">Char</span><span data-if="cpp" style="display:none">Char</span><span data-if="com" style="display:none">Char</span><span data-if="dotnet" style="display:none">charVal</span><span data-if="python" style="display:none">char</span></code></i></a> will contain the next byte.
Furthermore, 该算子 also emits a low-level error
message, when the read character cannot be transcoded without loss of
information into the current encoding of the HALCON library.
This can only happen when the file is UTF-8 encoded and the
current encoding of the HALCON library is <i><span data-if="hdevelop" style="display:inline">'locale'</span><span data-if="c" style="display:none">"locale"</span><span data-if="cpp" style="display:none">"locale"</span><span data-if="com" style="display:none">"locale"</span><span data-if="dotnet" style="display:none">"locale"</span><span data-if="python" style="display:none">"locale"</span></i>
(see <a href="set_system.html"><code><span data-if="hdevelop" style="display:inline">set_system(::'filename_encoding','locale':)</span><span data-if="c" style="display:none">set_system("filename_encoding","locale")</span><span data-if="cpp" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="com" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="dotnet" style="display:none">SetSystem("filename_encoding","locale")</span><span data-if="python" style="display:none">set_system("filename_encoding","locale")</span></code></a>).
</p>
<h2 id="sec_execution">运行信息</h2>
<ul>
  <li>多线程类型:可重入(与非独占操作符并行运行)。</li>
<li>多线程作用域:全局(可以从任何线程调用)。</li>
  <li>未经并行化处理。</li>
</ul>
<h2 id="sec_parameters">参数表</h2>
  <div class="par">
<div class="parhead">
<span id="FileHandle" class="parname"><b><code><span data-if="hdevelop" style="display:inline">FileHandle</span><span data-if="c" style="display:none">FileHandle</span><span data-if="cpp" style="display:none">FileHandle</span><span data-if="com" style="display:none">FileHandle</span><span data-if="dotnet" style="display:none">fileHandle</span><span data-if="python" style="display:none">file_handle</span></code></b> (input_control)  </span><span>file <code>→</code> <span data-if="dotnet" style="display:none"><a href="HFile.html">HFile</a>, </span><span data-if="dotnet" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="python" style="display:none">HHandle</span><span data-if="cpp" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="c" style="display:none">Htuple</span><span data-if="hdevelop" style="display:inline"> (handle)</span><span data-if="dotnet" style="display:none"> (<i>IntPtr</i>)</span><span data-if="cpp" style="display:none"> (<i>HHandle</i>)</span><span data-if="c" style="display:none"> (<i>handle</i>)</span></span>
</div>
<p class="pardesc">File handle.</p>
</div>
  <div class="par">
<div class="parhead">
<span id="Char" class="parname"><b><code><span data-if="hdevelop" style="display:inline">Char</span><span data-if="c" style="display:none">Char</span><span data-if="cpp" style="display:none">Char</span><span data-if="com" style="display:none">Char</span><span data-if="dotnet" style="display:none">charVal</span><span data-if="python" style="display:none">char</span></code></b> (output_control)  </span><span>string <code>→</code> <span data-if="dotnet" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="python" style="display:none">str</span><span data-if="cpp" style="display:none"><a href="HTuple.html">HTuple</a></span><span data-if="c" style="display:none">Htuple</span><span data-if="hdevelop" style="display:inline"> (string)</span><span data-if="dotnet" style="display:none"> (<i>string</i>)</span><span data-if="cpp" style="display:none"> (<i>HString</i>)</span><span data-if="c" style="display:none"> (<i>char*</i>)</span></span>
</div>
<p class="pardesc">Read character, which can be multi-byte or the control string
<i><span data-if="hdevelop" style="display:inline">'eof'</span><span data-if="c" style="display:none">"eof"</span><span data-if="cpp" style="display:none">"eof"</span><span data-if="com" style="display:none">"eof"</span><span data-if="dotnet" style="display:none">"eof"</span><span data-if="python" style="display:none">"eof"</span></i>.</p>
</div>
<h2 id="sec_example_all">例程 (HDevelop)</h2>
<pre class="example">
* Read a text file character by character.
open_file (FileName, 'input', FileHandle)
repeat
    fread_char (FileHandle, Char)
until (Char == 'eof')
close_file (FileHandle)
</pre>
<h2 id="sec_result">结果</h2>
<p>If an input file is open, 该算子 <code><span data-if="hdevelop" style="display:inline">fread_char</span><span data-if="c" style="display:none">fread_char</span><span data-if="cpp" style="display:none">FreadChar</span><span data-if="com" style="display:none">FreadChar</span><span data-if="dotnet" style="display:none">FreadChar</span><span data-if="python" style="display:none">fread_char</span></code> returns <TT>2</TT> (
      <TT>H_MSG_TRUE</TT>)
    .
Otherwise, an exception is raised.
Encoding errors have no influence on the result state.
</p>
<h2 id="sec_predecessors">可能的前置算子</h2>
<p>
<code><a href="open_file.html"><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></a></code>
</p>
<h2 id="sec_successors">可能的后置算子</h2>
<p>
<code><a href="close_file.html"><span data-if="hdevelop" style="display:inline">close_file</span><span data-if="c" style="display:none">close_file</span><span data-if="cpp" style="display:none">CloseFile</span><span data-if="com" style="display:none">CloseFile</span><span data-if="dotnet" style="display:none">CloseFile</span><span data-if="python" style="display:none">close_file</span></a></code>
</p>
<h2 id="sec_alternatives">可替代算子</h2>
<p>
<code><a href="fread_string.html"><span data-if="hdevelop" style="display:inline">fread_string</span><span data-if="c" style="display:none">fread_string</span><span data-if="cpp" style="display:none">FreadString</span><span data-if="com" style="display:none">FreadString</span><span data-if="dotnet" style="display:none">FreadString</span><span data-if="python" style="display:none">fread_string</span></a></code>, 
<code><a href="read_string.html"><span data-if="hdevelop" style="display:inline">read_string</span><span data-if="c" style="display:none">read_string</span><span data-if="cpp" style="display:none">ReadString</span><span data-if="com" style="display:none">ReadString</span><span data-if="dotnet" style="display:none">ReadString</span><span data-if="python" style="display:none">read_string</span></a></code>, 
<code><a href="fread_line.html"><span data-if="hdevelop" style="display:inline">fread_line</span><span data-if="c" style="display:none">fread_line</span><span data-if="cpp" style="display:none">FreadLine</span><span data-if="com" style="display:none">FreadLine</span><span data-if="dotnet" style="display:none">FreadLine</span><span data-if="python" style="display:none">fread_line</span></a></code>
</p>
<h2 id="sec_see">参考其它</h2>
<p>
<code><a href="open_file.html"><span data-if="hdevelop" style="display:inline">open_file</span><span data-if="c" style="display:none">open_file</span><span data-if="cpp" style="display:none">OpenFile</span><span data-if="com" style="display:none">OpenFile</span><span data-if="dotnet" style="display:none">OpenFile</span><span data-if="python" style="display:none">open_file</span></a></code>, 
<code><a href="close_file.html"><span data-if="hdevelop" style="display:inline">close_file</span><span data-if="c" style="display:none">close_file</span><span data-if="cpp" style="display:none">CloseFile</span><span data-if="com" style="display:none">CloseFile</span><span data-if="dotnet" style="display:none">CloseFile</span><span data-if="python" style="display:none">close_file</span></a></code>, 
<code><a href="fread_string.html"><span data-if="hdevelop" style="display:inline">fread_string</span><span data-if="c" style="display:none">fread_string</span><span data-if="cpp" style="display:none">FreadString</span><span data-if="com" style="display:none">FreadString</span><span data-if="dotnet" style="display:none">FreadString</span><span data-if="python" style="display:none">fread_string</span></a></code>, 
<code><a href="fread_line.html"><span data-if="hdevelop" style="display:inline">fread_line</span><span data-if="c" style="display:none">fread_line</span><span data-if="cpp" style="display:none">FreadLine</span><span data-if="com" style="display:none">FreadLine</span><span data-if="dotnet" style="display:none">FreadLine</span><span data-if="python" style="display:none">fread_line</span></a></code>
</p>
<h2 id="sec_module">模块</h2>
<p>
Foundation</p>
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